Near-Earth Objects (NEOs)—asteroids and comets that orbit the Sun near the Earth—pose serious threats to our planet. Approximately 1,000 discovered NEOs that are similar to the Chicxulub Impactor responsible for the Cretaceous–Paleogene Extinction Event roughly sixty-six million years ago are capable of causing regional or global devastation. Over 24,000 discovered NEOs that are similar to the Chelyabinsk Meteor—which impacted Russia in February 2013, damaged over 7,200 buildings, and injured more than 1,600 people—are capable of causing severe local or regional harm. And, in only the last five years, the number of discovered NEOs has nearly doubled.

One potential strategy to prevent an NEO–Earth impact is to change the NEO’s orbit. A state acting in good faith launches a spacecraft (called a gravity tractor) that orbits near the NEO in such a way that it pulls the NEO toward the spacecraft, gradually modifying the NEO’s orbit so that the NEO does not impact Earth. But the spacecraft’s mid-mission failure is possible. If the spacecraft is able to modify the NEO’s orbit only par-tially, then the NEO will still impact Earth, but it will impact a different state than if the spacecraft had done nothing. Worse yet, a state may deploy a gravity tractor in bad faith, hoping to deliberately redirect the NEO so that it impacts a different, particular state.

This Note analyzes whether, in these two scenarios, the redirecting state—that is, the state that launches and operates the gravity tractor—is liable to the state that the NEO impacts. Looking through the lens of international law, specifically the Liability Convention, the Outer Space Treaty, and the U.N. Charter, this Note concludes that a redirecting state that acts in good faith is liable to the impacted state under the Liability Convention and the U.N. Charter but not under the Outer Space Treaty. This Note then concludes that a redirecting state that acts in bad faith is liable to the impacted state under all three instruments.

Continue reading State Liability for Orbital Modification of a Near-Earth Object